Cite

Zones of Equal Temperature : mean minimum temperature [for the year].

MLA

Zones of Equal Temperature : Mean Minimum Temperature [for the Year]. A. Hoen & Co., Lith., 19AD. https://collections.library.yale.edu/catalog/15603705.

APA, 6th edition

Zones of Equal Temperature : mean minimum temperature [for the year]. (19 C.E.). [Maps]. A. Hoen & Co., Lith., https://collections.library.yale.edu/catalog/15603705.